3 VMA Mode
3.6 Occupied BW Measurement
Notes For numeric entries, the instrument chooses the nearest (arithmetically, on a linear scale, rounding
up) available VBW to the value entered. The 50MHz VBW is defined to mean “wide open”
The values shown in this table reflect the conditions after a Mode Preset
Dependencies Sometimes the displayed Video BW is not actually used to process the trace data:
When the Average detector is selected, and Sweep Type is set to Swept, the video bandwidth filter
cannot be used, because it uses the same hardware as the Average detector
When the Quasi-Peak, EMI Average, or RMS Average detector is selected, Video BW is implemented
by the digital IF as part of the detector
In this case, Video BW still acts to change the Sweep Time, if Sweep Time is in Auto, and still affects
the data on other traces for which this is not the case
Couplings Normally coupled to Res BW. If Video BW is set to Auto, then video bandwidth is changed as Res BW
changes, to maintain the preset ratio (normally 10:1)
Preset Auto, unless noted in "Video BW Presets" on page 987 below
ON
State Saved Saved in instrument state
Min 1 Hz
Max 50 MHz
Annunciation A “#” mark appears before “VBW” in the annotation when it is not coupled
Annotation In the bottom center of the screen, “VBW <value> <units>” indicates the current video bandwidth
value. Note that for some detectors this is not the value used for VBW (see above)
Backwards
Compatibility
Notes
For backwards compatibility, this command supports both BANDwidth and BWIDth forms
Video BW Presets
Unless noted in the table below, the Preset value is Auto.
Mode ID Preset Value
WCDMA 300 kHz
BT 30 kHz
RBW Filter Type
Selects the type for the resolution bandwidth filters. Historically, the Res BW filters
in HP/Agilent/Keysight spectrum analyzers were Gaussian filters, specified using the
–3dB bandwidth of the filter. That is, a 10MHz Res BW filter was a Gaussian shape
with its –3dB points 10MHz apart. In X-Series, you can choose between a Gaussian
and Flat Top filter shape, for varying measurement conditions.
987 Vector Modulation Analyzer Mode User's &Programmer's Reference
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